Many commercially important polymers are produced by suspension polymerization. The basic suspension polymerization process and the problems associated therewith are well known in the art, as discussed, for example, by Landoll in U.S. Pat. No. 4,352,916.
The use of hydrophobically modified water-soluble, nonionic cellulose ether polymers, such as hydrophobically modified hydroxyethyl cellulose (HMHEC), as stabilizers in the manufacture of polymers from vinyl monomers via suspension polymerization is disclosed in U.S. Pat. No. 4,352,916, cited above. Such stabilizers prevent the agglomeration of the polymer beads formed during suspension polymerization and also, to a large extent, help determine the final bead size distribution, polydispersity, and porosity. Their molecular weight, hydrophobe substitution level, hydrophobe length and concentration strongly influence the resulting polymer bead distribution in terms of average diameter and polydispersity. The stability of the suspensions prepared using such stabilizers is excellent, but broad bead size distribution occurs. Also, significant amounts of latex by-product (emulsion polymer) are produced. Thus, there is a need to provide suspension polymer beads of narrower Polydispersity and greater clarity (reduced cloudiness or haziness in the beads due to emulsion polymer by-product adsorption onto suspension polymer beads) than those obtained by suspension polymerization in the presence of such stabilizers.
An object of the present invention is to provide an improved suspension polymerization process for preparation of good yields of polymer beads of narrow polydispersity and superior clarity.
Another objective of the present invention is to minimize the amount of the latex by-product formed in the suspension polymerization processes.
A further objective of the present invention is to provide polymer beads of narrower polydispersity and greater clarity.
Other objectives of the present invention will become obvious from the above discussion and the following description of this invention.